Ring Imaging Research Articles

US and MRI anatomy of fetal ear

Introduction Fetal MRI has progressively become a major tool in prenatal imaging, and its complementary role towards ultrasound (US) is now widely accepted. Ultrasound is still the gold standard for prenatal imaging, but its capacity to rule out temporal bone pathology is limited. In contrast, MRI is capable of high spatial resolution, to study the development of the temporal bone structures during gestation. Indeed, it is possible to fully delineate the cochlea, vestibular apparatus (vestibule and semicircular canals), and the middle ear using MRI with T2-weighted sequences, as early as at gestation week (GW). Objectives Review basic US anatomic views of the evaluation of the fetal ears (external, middle and inner ear). Summarize the MRI sequences allowing good anatomical study. To trace US and MRI anatomy of the fetal ear. Results US anatomy of fetal ear: prenatal sonographic visualization of the fetal middle and inner ear is hampered by acoustic shadowing of the temporal bones. The inner ear: the most important limitation of sonographic fetal cochlear imaging is ossification of the temporal bones, which causes acoustic shadowing. We can see fetal cochlear using coronal head scanning through the mastoid fontanel or squamous suture. Middle ear: ossicle (incus and malleus) are observed only in the second half of pregnancy. They appeared as a bright echo within the upper part of the tympanic ring in. External ear: US can help auricular detection of two ears which is better in 20–24 weeks and can be considered as the best period to detect external ear abnormalities. Prenatal tympanic ring imaging in US is more feasible in the second-trimester examinations. Tympanic rings appear as distinct, thin, circular structures lying on the infero-lateral surface of the fetal skull. MRI anatomy of fetal ear: – sequences: all fetal cerebral magnetic resonance imaging (MRI) examinations performed at 1.5 Tesla. We review T2-W axial, sagittal and coronal images. The external, middle and inner ears were respectively evaluated. Fetuses presenting with a facial and/or cerebral malformation were excluded; – MRI anatomy: contrary to sonography, the contribution of MRI in the prenatal diagnosis of middle and inner ear abnormalities has been investigated in recent years; – inner ear: the ability to identify the inner structure of the cochlea improved with gestational age, is related to a progressive gain of T2 contrast against the surrounding otic capsule as it ossifies, and not to the cochlear development itself that is supposed to be fully complete. The T2-weighted MRI images showed a high signal intensity of fluid in the membranous labyrinth, which, at 14 weeks, was the first recognizable fetal temporal bone structure; – middle ear: visualization of the middle ear with fetal MRI can be visualized after 25 week. The ossicles are seen as a T2-hypointense area, never with enough detail to discriminate each ossicle. The tympanic cavity is always well-demonstrated on axial and coronal T2-W slices; – external ear: the external ears (EA) are normally only patent after 28 gestation week, after the progressive involution of an ectodermal plug that occludes them until then. Conclusion MRI represents the most important tool for fetal ear exploration and the knowledge of its anatomy may lead to a better understanding of congenital ear disorders.

Particle identification performance of the prototype aerogel RICH counter for the Belle II experiment

We have developed a new type of particle identification device, called an Aerogel Ring Imaging Cherenkov (ARICH) counter, for the Belle II experiment. It uses silica aerogel tiles as Cherenkov radiators. For detection of Cherenkov photons, Hybrid Avalanche Photo-Detectors (HAPDs) are used. The designed HAPD has a high sensitivity to single photons under a strong magnetic field. We have confirmed that the HAPD provides high efficiency for single-photon detection even after exposure to neutron and gamma-ray radiation that exceeds the levels expected in the 10-year Belle II operation. In order to confirm the basic performance of the ARICH counter system, we carried out a beam test at the DESY using a prototype of the ARICH counter with six HAPD modules. The results are in agreement with our expectations and confirm the suitability of the ARICH counter for the Belle II experiment. Based on the in-beam performance of the device, we expect that the identification efficiency at 3.5 GeV/c is 97.4% and 4.9% for pions and kaons, respectively. This paper summarizes the development of the HAPD for the ARICH and the evaluation of the performance of the prototype ARICH counter built with the final design components.

Effect of Data Pre-processing on Super-Resolution reconstruction and Pattern Recognition

Super-resolution (SR) fluorescence microscopy has emerged as a powerful tool for characterizing biological systems with unprecedented detail. New developments in both fluorophores and detection techniques and tools are pushing this technique further into the realm of 3D imaging and visualization of dynamic processes. An important set of the super-resolution techniques are those based on fluorophores that switch between on- and off-states in a random/stochastic manner. All of these techniques require significant data processing in order to reconstruct the super-resolved image. Processing of the raw data is therefore a critical step that, if done incorrectly, can give rise to fictitious features and underestimation of errors. One key parameter calculated from the raw data is the localization error based on the photon counts for each fluorophore. Here, we explore different pre-processing approaches and their effect on localization error and reconstructed super-resolved images derived from multi-colour dSTORM datasets. These datasets presented differences in background levels and dynamics, which allowed us to evaluate the effect of both spatial and temporal filtering. The application of these tools and techniques for super-resolution imaging of ring- and filament structures in cells will be specifically emphasized.

The upgraded LHCb RICH detector: Status and perspectives

The LHCb upgrade will take place during the second long shutdown of the LHC (LS2). The upgrade will enable the experiment to run at an instantaneous luminosity of 2×1033cm−2s−1 and will read out data at a rate of 40MHz into a flexible software-based trigger. The two Ring Imaging Cherenkov detectors (RICH), installed in the LHCb experiment, will be re-designed to comply with these new operating conditions. The status and perspective of the RICH upgrade project will be presented.

Evaporation-induced self-assembly of quantum dots-based concentric rings on polymer-based nanocomposite films.

The "ball-on-film" template is used to construct concentric rings on the surface of PMMA-QDs (polymethyl methacrylate - quantum dots) nanocomposite films via the evaporation of pure chloroform droplets, which are confined by a steel ball. The concentric rings consist of QDs, as revealed by the fluorescence images of the concentric rings. The photoluminescence intensity of the concentric rings increases with the increase of the distance to the ball center, suggesting that the amount of QDs accumulated around the contact line at individual stick state increases with the increase of the distance to the ball center. Both the wavelength and cross-sectional area (width) of the concentric rings increase approximately linearly with increasing distance to the ball center, independent of the ball size, the film thickness and the QDs concentration. For the PMMA-QDs nanocomposite films prepared from the same QDs concentration in chloroform, the thicker the PMMA-QDs nanocomposite film, the larger the wavelength for the same distance to the ball center. The effect of confinement of two steel balls on the surface patterns over the PMMA-QDs nanocomposite films is studied via a template of "two spheres on film". Symmetric surface patterns are formed. There exist two types of featureless zone between the two balls, depending on the distance between the two balls: one is the inner featureless zone and the other is the outer featureless zone. The size of both featureless zones increases with the increase of the ball distance.

Superconducting 72-pole Indirect Cooling 3Tesla Wiggler for CLIC Damping Ring and ANKA Image Beamline

One of the directions of BINP activity is the creation of multipole superconducting wigglers with the magnetic field levels from 2 T to 7.5 T which are installed on many SR sources. Special efforts were made by BINP to develop the cryogenic system with zero liquid helium consumption. The next significant step became the design and creation of superconducting full size prototype of damping wiggler for CLIC project where supposed the installation of 104 wigglers. For operation of CLIC damping wiggler it is required the magnetic field of 3 T and the period about 50 mm with a beam vertical aperture of 13 mm. Design features of the wiggler which was proposed and created by BINP is the application of the indirect cooling method. In this case Nb-Ti magnet with the length of 1.9 m and the weight of 700 kg is located in a vacuum and is cooled by four Gifford-McMahon cryocoolers. To maintain the temperature about 4.2K on the magnet it is used the tubes with circulating liquid helium as the heat conducting elements. To increase the efficiency of pre-cooling down of the magnet it is used nitrogen-based heat pipes of siphon type. The features of the magnetic and cryogenic systems of CLIC damping wiggler full size prototype and test results are presented in this article.

LHCb RICH Upgrade: an overview of the photon detector and electronic system

The LHCb experiment is one of the four large detectors operating at the LHC at CERN and it is mainly devoted to CP violation measurements and to the search for new physics in rare decays of beauty and charm hadrons. The data from the two Ring Image Cherenkov (RICH-1 and RICH-2) detectors are essential to identify particles in a wide momentum range. From 2019 onwards 14 TeV collisions with luminosities reaching up to 2 × 1033 cm−2s−1 with 25 ns bunch spacing are planned, with the goal of collecting 5 fb−1 of data per year. In order to avoid degradation of the PID performance at such high rate (40 MHz), the RICH detector has to be upgraded. New photodetectors (Multi-anode photomultiplier tubes, MaPMTs) have been chosen and will be read out using an 8-channel chip, named CLARO, designed to sustain a photon counting rate up to 40 MHz, while minimizing the power consumption and the cross-talk. A 128-bit digital register allows selection of thresholds and attenuation values and provides features useful for testing and debugging. Photosensors and electronics are arranged in basic units, the first prototypes of which have been tested in charged particle beams in autumn 2014. An overview of the CLARO features and of the readout electronics is presented.

Search for long-lived heavy charged particles using a ring imaging Cherenkov technique at LHCb.

A search is performed for heavy long-lived charged particles using 3.0 {rm fb}^{-1} of proton–proton collisions collected at sqrt{s}= 7 and 8 TeV with the LHCb detector. The search is mainly based on the response of the ring imaging Cherenkov detectors to distinguish the heavy, slow-moving particles from muons. No evidence is found for the production of such long-lived states. The results are expressed as limits on the Drell–Yan production of pairs of long-lived particles, with both particles in the LHCb pseudorapidity acceptance, 1.8 < eta < 4.9. The mass-dependent cross-section upper limits are in the range 2–4 fb (at 95 % CL) for masses between 14 and 309 {mathrm {,GeV!/}c^2}.

Novel real-time alignment and calibration of the LHCb detector in Run II

An automatic real-time alignment and calibration strategy of the LHCb detector was developed for the Run II. Thanks to the online calibration, tighter event selection criteria can be used in the trigger. Furthermore, the online calibration facilitates the use of hadronic particle identification using the Ring Imaging Cherenkov (RICH) detectors at the trigger level. The motivation for a real-time alignment and calibration of the LHCb detector is discussed from both the operational and physics performance points of view. Specific challenges of this novel configuration are discussed, as well as the working procedures of the framework and its performance.

Subsurface structure of a maar–diatreme and associated tuff ring from a high-resolution geophysical survey, Rattlesnake Crater, Arizona

Geophysical survey techniques including gravity, magnetics, and ground penetrating radar were utilized to study the diatreme and tuff ring at Rattlesnake Crater, a maar in the San Francisco Volcanic Field of northern Arizona. Significant magnetic anomalies (+1600nT) and a positive gravity anomaly (+1.4mGal) are associated with the maar. Joint modeling of magnetic and gravity data indicate that the diatreme that underlies Rattlesnake Crater has volume of 0.8–1km3, and extends to at least 800m depth. The modeled diatreme comprises at least two zones of variable density and magnetization, including a low density, highly magnetized unit near the center of the diatreme, interpreted to be a pyroclastic unit emplaced at sufficiently high temperature and containing sufficient juvenile fraction to acquire thermal remanent magnetization. Magnetic anomalies and ground penetrating radar (GPR) imaging demonstrate that the bedded pyroclastic deposits of the tuff ring also carry high magnetization, likely produced by energetic emplacement of hot pyroclastic density currents. GPR profiles on the tuff ring reveal long (~100m) wavelength undulations in bedding planes. Elsewhere, comparable bedforms have been interpreted as base surge deposits inflated by air entrainment from eruption column collapse. Interpretation of these geophysical data suggests that Rattlesnake Crater produced highly energetic phreatomagmatic activity that gave way to less explosive activity as the eruption progressed. The positive gravity anomaly associated with the maar crater is interpreted to be caused by coherent bodies within the diatreme and possibly lava ponding on the crater floor. These dense magnetized bodies have excess mass of 2–4×1010kg, and occupy approximately 5% of the diatreme by volume. Magnetic anomalies on the crater floor are elongate NW–SE, suggesting that the eruption may have been triggered by the interaction of ascending magma with water in fractures of this orientation. GPR imaging of the tuff ring also suggests that substantial land-slip may have occurred on the western rim, perhaps causing part of the tuff ring to collapse into the crater. Strong radar reflections indicative of well-developed weathering horizons are present as well. The techniques employed at Rattlesnake Crater demonstrate the value of combining multiple geophysical techniques in areas where exposures are limited and invasive exploration is not an option.

Characterization of the Hamamatsu H12700A-03 and R12699-03 multi-anode photomultiplier tubes

The H12700 is a novel 64-channel 52 × 52 mm2 square Multi-Anode PhotoMultiplier Tube (MaPMT) produced by Hamamatsu. Its characteristics make this device suitable for high energy physics applications, such as in Ring Imaging Cherenkov (RICH) detectors. Hamamatsu provides the H12700 tube with an embedded socket connecting the anodes to the output pins and including an active voltage divider. A second device version, the R12699, is also available and differs from the former by the absence of the socket. This paper describes a complete characterization of both models, starting from the standard operating parameters (single photon spectra, average gain, anode uniformity and dark current value), investigating in detail the cross-talk effect among neighbouring pixels and considering the behaviour in critical environment conditions, such as in presence of a static magnetic field up to 100 Gauss, at different operating temperatures and after long exposure to intense light.

Small particles dominate Saturn's Phoebe ring to surprisingly large distances.

Saturn's faint outermost ring, discovered in 2009 (ref. 1), is probably formed by particles ejected from the distant moon Phoebe. The ring was detected between distances of 128 and 207 Saturn radii (RS = 60,330 kilometres) from the planet, with a full vertical extent of 40RS, making it well over ten times larger than Saturn's hitherto largest known ring, the E ring. The total radial extent of the Phoebe ring could not, however, be determined at that time, nor could particle sizes be significantly constrained. Here we report infrared imaging of the entire ring, which extends from 100RS out to a surprisingly distant 270RS. We model the orbital dynamics of ring particles launched from Phoebe, and construct theoretical power-law profiles of the particle size distribution. We find that very steep profiles fit the data best, and that elevated grain temperatures, arising because of the radiative inefficiency of the smallest grains, probably contribute to the steepness. By converting our constraint on particle sizes into a form that is independent of the uncertain size distribution, we determine that particles with radii greater than ten centimetres, whose orbits do not decay appreciably inward over 4.5 billion years, contribute at most about ten per cent to the cross-sectional area of the ring's dusty component.

Quenching the scintillation in CF4 Cherenkov gas radiator

CF4 is used as a Cherenkov gas radiator in one of the Ring Imaging Cherenkov detectors at the LHCb experiment at the CERN Large Hadron Collider. CF4 is well known to have a high scintillation photon yield in the near and far VUV, UV and in the visible wavelength range. A large flux of scintillation photons in our photon detection acceptance between 200 and 800nm could compromise the particle identification efficiency. We will show that this scintillation photon emission system can be effectively quenched, consistent with radiationless transitions, with no significant impact on the photons resulting from Cherenkov radiation.

Investigation of Hamamatsu H8500 phototubes as single photon detectors

We have investigated the response of a significant sample of Hamamatsu H8500 MultiAnode PhotoMultiplier Tubes (MAPMTs) as single photon detectors, in view of their use in a ring imaging Cherenkov counter for the CLAS12 spectrometer at the Thomas Jefferson National Accelerator Facility. For this, a laser working at 407.2nm wavelength was employed. The sample is divided equally into standard window type, with a spectral response in the visible light region, and UV-enhanced window type MAPMTs. The studies confirm the suitability of these MAPMTs for single photon detection in such a Cherenkov imaging application.

Spectroscopy ofLiΛ9by electroproduction

In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei can provide information on the details of the effective hyperon-nucleon interaction. Electroproduction of the hypernucleus Lambda-9Li has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a 9Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a Ring Imaging CHerenkov detector (RICH) were added to the Hall A standard equipment. The cross section to low-lying states of Lambda-9Li is concentrated within 3 MeV of the ground state and can be fitted with four peaks. The positions of the doublets agree with theory while a disagreement could exist with respect to the relative strengths of the peaks in the doublets. A Lambda separation energy of 8.36 +- 0.08 (stat.) +- 0.08 (syst.) MeV was measured, in agreement with an earlier experiment.

Backtracking algorithm for lepton reconstruction with HADES

The High Acceptance Di-Electron Spectrometer (HADES) at the GSI Helmholtzzentrum für Schwerionenforschung investigates dilepton and strangeness production in elementary and heavy-ion collisions. In April - May 2012 HADES recorded 7 billion Au+Au events at a beam energy of 1.23 GeV/u with the highest multiplicities measured so far. The track reconstruction and particle identification in the high track density environment are challenging. The most important detector component for lepton identification is the Ring Imaging Cherenkov detector. Its main purpose is the separation of electrons and positrons from large background of charged hadrons produced in heavy-ion collisions. In order to improve lepton identification this backtracking algorithm was developed. In this contribution we will show the results of the algorithm compared to the currently applied method for e+/-identification. Efficiency and purity of a reconstructed e+/- sample will be discussed as well.

Influence of wavelength-shifting films on multianode PMTs with UV-extended windows

Wavelength-shifting (WLS) films were applied on UV-extended front windows of multianode photomultiplier tubes (MAPMTs) in order to increase the sensitivity of the MAPMTs at shorter wavelengths. The WLS material contained p-Terphenyl as photoactive component, which absorbs shorter wavelength photons (<300nm) and re-emits fluorescence photons around 350nm, i.e., at the maximum of the PMTs׳ sensitivity. The films were applied by means of dip-coating and the film performance was studied with respect to quantum efficiency, film homogeneity, and crosstalk on the MAPMTs. Using WLS-film-covered MAPMTs in a gaseous Ring Imaging Cherenkov detector, the number of detected photoelectrons per ring increased by up to 21% in an in-beam test.

Whole Genome Sequence Analysis of Salmonella Enteritidis PT4 Outbreaks from a National Reference Laboratory's Viewpoint.

Introduction: In April and May 2014, two suspected egg-related outbreaks of Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) were investigated by the Belgian National Reference Laboratory of Foodborne Outbreaks. Both the suspected food and human isolates being available, and this for both outbreaks, made these the ideal case study for a retrospective whole genome sequencing (WGS) analysis with the goal to investigate the feasibility of this technology for outbreak investigation by a National Reference Laboratory or National Reference Centre without thorough bioinformatics expertise.Methods: The two outbreaks were originally investigated epidemiologically with a standard questionnaire and with serotyping, phage typing, multiple-locus variable-number of tandem repeats analysis (MLVA) and antimicrobial susceptibility testing as classical microbiological methods. Retrospectively, WGS of six outbreak isolates was done on an Illumina HiSeq. Analysis of the WGS data was performed with currently available, user-friendly software and tools, namely CLC Genomics Workbench, the tools available on the server of the Center for Genomic Epidemiology and BLAST Ring Image Generator (BRIG).Results: To all collected human and food outbreak isolates, classical microbiological investigation assigned phage type PT4 (variant phage type PT4a for one human isolate) and MLVA profile 3-10-5-4-1, both of which are common for human isolates in Belgium. The WGS analysis confirmed the link between food and human isolates for each of the outbreaks and clearly discriminated between the two outbreaks occurring in a same time period, thereby suggesting a non-common source of contamination. Also, an additional plasmid carrying an antibiotic resistance gene was discovered in the human isolate with the variant phage type PT4a.Discussion: For the two investigated outbreaks occurring at geographically separated locations, the gold standard classical microbiological subtyping methods were not sufficiently discriminative to distinguish between or assign a common origin of contamination for the two outbreaks, while WGS analysis could do so. This case study demonstrated the added value of WGS for outbreak investigations by confirming and/or discriminating food and human isolates between and within outbreaks. It also proved the feasibility of WGS as complementary or even future replacing (sub)typing method for the average routine laboratory.

Development of the micro-channel plate photomultiplier for the Belle II time-of-propagation counter

The time-of-propagation counter for the Belle II experiment is a new particle identification device using ring imaging Cherenkov technique. In order to detect each Cherenkov photon with a timing precision of 30–40ps in a 1.5T magnetic field, a micro-channel plate photomultiplier tube is a suitable device for the TOP counter. By introducing an atomic layer deposition technique on the micro-channel plate surface, the tube lifetime was improved by a factor of 3–10 relative to more conventional devices. A total of 530 tubes have been produced. To ensure appropriate tube performance, the quantum efficiency, gain and transit time spread have been measured for all units. The results from each measurement are discussed. Results from a beamtest with a 2GeV/c positron beam are also reported and demonstrate the good tube performance.

Characterization of the Hamamatsu MPPC S11834 as photon sensor for RICH

Recent development of SiPMs makes them a promising candidate for replacement of photomultiplier tubes in Ring Imaging Cherenkov (RICH) counters. A commercially available 8×8 SiPM array, Hamamatsu MPPC S11834 with a rather low dark count rate, was tested as a single photon sensor in a RICH counter. To increase its overall geometrical acceptance, light concentrators were employed. The various factors that influence their efficiency are estimated and the results of measurements with polarized light are presented, showing a good agreement with a Monte Carlo study.